1. Field of the Invention
The present invention relates, in general, to an acoustic system for detecting insects in agricultural commodities. The terms "insect" and "insects" are used herein as including adult insects, insect larvae, etc. The terms "commodity" and "commodities" are used herein as including cotton bolls, fruit, nuts, grain, wood, etc.
2. Information Disclosure Statement
Acoustic detection of insects in agricultural commodities such as grain, fruit, nuts, and wood has been known for a number of years.
The destruction caused by insects in harvested commodities is significant. About 10% of grain in the United States of America (U.S.) is destroyed by insects annually. Overseas the percentage is much higher, especially in Africa and parts of Asia. Importation of fruit containing insect larvae can cause infestations that are destructive to domestic fruit crops. Major efforts are made by the United States Department of Agriculture (USDA) to control infestations of the Mediterranean fruit fly in California and Florida. Fruit imported into the U.S. from countries suspected of being infested with quarantine insects is inspected by cutting samples open and searching for larvae. This method is time consuming, subject to human error, and destructive of fruit. The export of fruit and grain is similarly affected by insect infestations. Overseas importers often require exacting standards to ensure that fruit contains no quarantine insect larvae and that grain infestations are within defined limits.
Another agricultural problem is the destruction of cotton crops caused by insects such as the boll weevil and the pink bollworm. Major efforts are made by cotton growers in California, with the aid of USDA Animal Plant and Health Inspection Service scientists, to control the pink bollworm. Cotton bolls are gathered from the fields to detertmine if there is a pink bollworm infestation. The bolls are cut open and inspected in the same way as fruit. Again, this is time consuming and inefficient.
A preliminary patentability search in Class 73, subclasses 587 and 661, produced the following patents which are believed to be relevant to the present invention:
Shade et al., U.S. Pat. No. 4,809,554, issued Mar. 7, 1989, discloses an insect detector that uses an ultrasonic detecting device sensitive to frequencies in the 40,000 hertz range. Ultrasonic means above the frequency range of human hearing (20 to 20,000 hertz).
Because sound waves are strongly attenuated in grain at high frequencies, it is unlikely that the ultrasonic detector can detect insects in grain at distances more than a few millimeters.
Pallaske, U.S. Pat. No. 4,941,356, issued Jul. 17, 1990, discloses a process for detecting the presence of adult insects or insect larvae in a solid substrate such as wood. The process includes the steps of recording the vibration or noise caused by insects in the substrate, converting the recorded vibration or noise to digital form, and then comparing the digital data to reference data obtained by applying noise or vibration behavioral reference pattern data to a microcomputer. Pallaske is concerned with the signal analysis used to detect insects in solids such as wood, and to distinguish the insect sounds from other sounds. The drawings consist of flow charts with little indication of the hardware used.
Betts, U.S. Pat. No. 4,991,439, issued Feb. 12, 1991, discloses an apparatus for detecting the presence of insects in particulate matter having a vibration receiving structure physically contacting in an off-center location, a piezoelectric transducer structure, such as a crystal, for directly detecting the vibration in the particulate matter.
The principle of the sounding rod is used to detect insects within a body of grain. Longitudinal waves travel up the rod exciting an electrical response in the piezoelectric structure. The rod is sensitive mainly at its end which appears to have a relatively small surface area to receive sound waves from insects.
Additionally, the following patents are known to the inventors and are believed to be relevant to the present invention:
Betts, U.S. Pat. No. 4,895,025, issued Jan. 23, 1990, discloses an apparatus for non-invasively detecting the presence of hidden insects actively destroying an article. The apparatus includes a piezoelectric transducer which generates electrical signals in response to mechanical forces applied thereto, a probe or diaphragm in direct contact with the piezoelectric transducer and with the article for detecting vibration forces in the article and transferring such forces to the piezoelectric transducer, an amplifier for amplifying the portion of the electrical signals produced by the piezoelectric transducer represented by insects which may inhabit the article, and means for analyzing the electrical signals representative of the vibrations to identify the species within the article.
Litzkow et al., U.S. Pat. No. 4,671,114, issued Jun. 9, 1987, discloses an apparatus for detecting insect larvae in agricultural commodities. The apparatus includes at least one sound-detecting diaphragm for holding an agricultural commodity, a sound waveguide connected at one end to the diaphragm for conveying sound waves from the diaphragm, a transducer connected to the other end of the waveguide for converting sound waves in the waveguide to electrical signals, an amplifier for amplifying the electrical signals; and signal observation means connected to the amplifier for allowing the output of the amplifier to be observed. The waveguide in this apparatus tends to have a detrimental effect because it acts as a resonator distorting the insect sounds.
Litzkow et al., U.S. Pat. No. 4,937,555, issued Jun. 26, 1990, discloses an apparatus for detecting insect infestation in agricultural commodities. The apparatus may include a container for containing the agricultural commodity or a probe for being inserted into the agricultural commodity, and a piezoelectric means located with the container or attached to the probe for being placed in direct communication with the agricultural commodity and for generating electricity in response to vibration only of a frequency above about 500 hertz. It should be noted that placing the hard, plane piezoelectric surface in direct contact with grain, fruit, cotton boll or other agricultural commodity does not provide as good an interfacial acoustic match as the diaphragm or liquid-filled cushion in our invention. Also the piezoelectric becomes less sensitive with pressure, such as would occur deep inside a grain silo.
None of the above identified patents or prior art discloses or suggests the present invention. More specifically, nothing in the known prior art discloses or suggests an apparatus for detecting insects in agricultural commodities including isolation means for isolating the agricultural commodities from external noise and vibration; sensitive acoustic sensor means for detecting any sound from the agricultural commodities and for generating a signal in response to any sound so detected; and user recognizable output means for producing user recognizable output in response to signals generated by the acoustic sensor means.